(1) Field of the Invention
The present invention relates generally to the method of fabricating micro-machined micro-mirror switching device and more particularly to fabricate metallic mirrors on single crystal silicon substrate.
(2) Description of the Prior Art
After its first conception in the 80's as a display device, MEMS (micro electro-mechanical system) micro-mirrors have come a long way in revolutionizing the data transport in communication networks. This area has been of particular interest for people involved in MEMS, in the past ten years. Micro-mirror devices have applications in display devices as a pixel, scanner type of display device. Light beam steering using micro-mirrors is being exploited in optical communication networks. MEMS based optical cross connect devices are being used in long haul networks to select and switch the light data signals without converting them to electronic domain. A large number of micro-mirror designs and mechanisms have been proposed. Surface micro machining is the most commonly used method for fabricating micro-mirror devices. Thin films such as poly-silicon, silicon dioxide, silicon nitride, and metal films such as aluminum, gold, chromium, and titanium have been used to develop micro-mirror devices for various applications. Some other researchers have used silicon-on-oxide MEMS, deep RIE SCREAM process, and in some cases backside aqueous potassium hydroxide etching to fabricate micro-mirror devices. In most devices, torsion springs or free hinges together with comb-drive or gap closing electrostatic actuators have been used.
U.S Pat. No. 5,537,083 describes a micro mechanical filter having planar components and fabricated using integrated circuit micro fabrication techniques. The mechanical coupling between input and output transducers includes planar fixtures, displacement of the electrodes producing bending of the elements of the fixtures. Processes include depositing electrical signal processing circuitry on a substrate, depositing interface components between signal processing circuitry and a mechanical filter in a first layer; depositing in a second layer components of the mechanical filter.
U.S. Pat. No. 5,999,303 describes an optical head utilizing a micro machined element in combination with a light source and a lens to read and write data onto a storage disk. A micro-machined element may include a tethered steerable micro-machined mirror. A movement of the micro machined mirror alters a beam of laser light transmitted from the light source to the optical head and a reflected light beam from the storage disk.
U.S. Pat. No. 6,210,988 B1 relates to micro-electromechanical systems using silicon-germanium films. The process includes depositing a sacrificial layer of silicon-germanium (SiGe) onto the substrate; depositing a structural layer of SiGe onto the sacrificial layer, where the germanium (Ge) content of the sacrificial layer is greater than the Ge content of the structural layer; and removing at least a portion of the sacrificial layer.